2002 XR400R weepy head gasket woes...


Recently picked up a '02 XR400R. Pretty clean, very few mods (airbox, skidplate, handguards, etc). Stock bars, stock front tire, stock exhaust, easy to start, runs well, fork seals good, no weird top-end noises, or visible leaks, etc. Did oil/filter change (Maxima 20-50 conventional), new plug, had valves checked at reputable local shop (in spec), carb clean/re-jet/new needle, and got a wiring issue sorted. During a meticulous toothbrush cleaning job, I noticed some dirt/grease around the (steel, presumably OEM) head gasket. The weather has been getting rather warm here in central AZ, and after a hour or so ride, I'll have a small amount (couple of drops-literally) of oil on the top of the upper most cylinder cooling fin, on the front-left "corner", just to the left of the exhaust manifold. I've also noticed a tiny amount of oil weeping from the head gasket on the left hand side. Again, we're talking a very small amount. Fold a shop towel in half, wipe, and it's gone. Oil level stays consistent. I didn't notice the weeping before my obsessive/compulsive cleaning job, as the small amount of dirt that had accumulated between the cooling fins seemed to do a good job of hiding the problem.

Here's my question: It's a 10 year old bike that I've got about $2500 into. Should I just ride the thing, and keep an eye on it, or do I need to consider replacing the head gasket immediately. I assume I would also need to replace the valve cover gasket as well, as this would have to come off to access the head bolts. While we're at it, would I need to have the head and/or cylinder re-surfaced to ensure a proper seal? Since it'll be apart, should I consider a new piston and rings? Big bore kit? Somebody please stop me before I go crazy!

Any advice would be most sincerely appreciated.


Good on you for going over a bike that is new to you so meticulously. You find a lot of little things to become aware of before they become big problems that way.

At this point, with no more seepage than you're seeing( a piddly amount), if the leak isn't effecting engine performance, causing carb/jetting issues, vacuum leaks, etc., I'd let it go and just watch it.

Knowing how the bike was ridden, if properly tuned and taken care/maintained by the PO can help you determine if it has the mileage and wear associated with needing a top end job. If compression seems good and it's doesn't get mistaken for a 2 stroke from a bunch of smoke constantly coming out of the tailpipe, I'd say it's good to go.

While you're being so meticulous, remove the swingarm bolt and grease it. Check your frame over for cracks, particularly under the seat.

Now go ride and have fun. You bought a great bike.

Thank you for the reply.

It's nice to have someone else's perspective. Does anyone have an opinion about whether or not switching from synthetic to conventional would exacerbate a gasket/seal leak? I vaguely recollect the previous owner mention that he used Honda HP4. As soon as I got the bike home, I dumped the old oil and filter (funky, looks like it had been sitting for quite some time, or had gotten wet) and put in Maxima 20-50 conventional. Ran it for about a hundred miles, and did another oil/filter change, with the same type/brand of oil. Currently have about 100 or so miles on that oil change. Spotless. Just clean and clear, and right where it's supposed to be on the dipstick. Doesn't smoke at all. Runs great. I've heard conflicting reports about conventional vs synthetic in XR400Rs. Anyone care to chime in?

Thanks again!

just adding, the hp4 is the honda's synthetic oil which I never tried. But just as an input, my 400 get the honda gn4 10w40 black after only 2 full tanks and the shell rotella T 15w40 was still golden-brown after 6 fuel tanks and is way cheaper!!!

I use synthetic oil in all our xrs it stays cleaner longer by 3times.Also if its Hot,your running your bike hard it runs cooler.For you small head gasket leak.If only small amount(only oil not Comp leak).Lay the bike on its side,get a can of brake clean,small brush.Spray and clean.Put black silicon 1/4 inch thick,from one fin to the other where head gaskit is.Go about 3-4 in around sides.It will last and not leak.On my motor I forgot to put the small side bolts,in the head.Mine leaked left side.I did that trick,lasted over 10-12 years.Then took apart motor, to put new piston in.Found out I left out the two bolts.The two bolts where still in my parts box after 10-12 years.Sometimes REAL BONE HEAD.

Also I forgot to add dont use the honda oil.I have had problems with this oil.Also honda factory riders I know do not use it.

Time to bump and old thread :)


I've got exactly the same issue as OP, I'm thinking there's no point to fixing it ATM.

Recently I had exhaust and carby off and checked valve condition with my bore scope and they all look good, same with piston crown.

So no need to pull head for reco.


Would there be any point to tightening/checking head stud/bolt torque? Also what torque should it be? 




you could certainly pull the valve cover off and verify head torque, 33ft/lbs is spec.

I had this problem on my 250.  Two of the threads in the cylinder were slightly stripped.  They torqued to spec each time I installed the head but soon there was a leak.  


The only way to detect this problem (other than the leak) is to check torque before disassembly.  



The solution was a new cylinder.  You could also repair the threads.  I replaced the bolts as well.

XR4's don't need no stinking bolts,,,,,,,,,,,,,,,,,just pour some Rotella in there and ride!

I always used Honda oil Never had any problems 0n my XR400 2004 did a lot of multi day Dualsport rides many miles from 04 to 09 was runing like a champ when I sold it I maintain my sons 2002 XR400 same way good luck xrs are awesome bikes

If you have never had problems with Honda oil,keep using it. We tend to push our Xrs in Baja real hard.We had shifting problems,when hot.Also wide open 250 6th gear/xr4 5th.They would down shift,without moving shift lever. Like I said no Honda factory would ever use Honda Oil.All problems we had went away,by not using Honda oil.BTR

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